Building structures often incorporate expansion joints to accommodate the movement of structural elements as a result of temperature changes or seismic activity. Local building codes in addition often require expansion joints to meet minimum requirements for fire resistance. This means that the fire barrier assembly used to close the expansion joint opening must not only be capable of accommodating movement, but must in addition be capable of resisting flame penetration while limiting heat rise through the joint to the level prescribed in the code. When the expansion joint is part of the building envelope it must also be weather proof.
Prior attempts to provide suitable fire barrier assemblies have not been satisfactory from an economical point of view because they are either too costly to manufacture or too labor intensive to install. An example of prior art methods of providing a weather proof fire resistant expansion joint can be found in U.S. Pat. No. 4,517,779 to Dunsworth. This patent discloses a joint cover comprising a hollow barrier which allows the relatively movable structural elements beneath it to slide along the bottom surface of the cover. The hollow cavity of the cover contains a hygroscopic material that releases coolant liquid by a wicking process when the barrier assembly is exposed to high temperatures. In addition, a separate smoke barrier in the form of flexible refractory cloth is employed. It is apparent that an installed assembly of this type is quite expensive.
A simpler arrangement is disclosed in U.S. Pat. No. 4,566,242 to Dunsworth wherein a slide plate covers the void between adjacent floors in an internal expansion joint assembly. A refractory fiber cloth jacket functions as a smoke barrier and as a support for refractory insulation which acts as a heat barrier. While this arrangement is considerably simpler in design and less expensive than the assembly of U.S. Pat. No. 4,517,779, it is designed for use as an internal expansion joint rather than an external expansion joint, is not weather resistant, and requires the refractory cloth and insulation to be quite wide in order to extend out to the lower legs of the clamping brackets 22 and 24. This results in the smoke and heat barrier assembly costing still more than desired. Further, the installation of the assembly, which requires the clamping brackets to be bolted to the floor sections and the grout faces, is still more labor intensive than desired. In addition, penetration of the refractory material by the bolts introduces an unwanted source of heat transmission.
It would obviously be beneficial to have a fire resistant expansion joint design which not only performs the functions required of it but which also has a relatively low installed cost as a result of economies of manufacture and the ability to rapidly install the system.